1. Field of the Invention
The present invention relates generally to a data communication apparatus and method in a mobile communication system, and in particular, to an apparatus and method for assigning a supplemental channel (SCH) to service data communication in a high-speed radio communication network.
2. Description of the Related Art
Cellular systems have been developed to provide diverse high-speed data services as well as voice service in the mobile communication industry. As a main example, the future mobile communication systems will provide an improved method of efficiently assigning high-speed radio traffic channels to service information over high-speed radio communication networks such as IMT2000, cdma2000, W-CDMA, UMTS, GPRS, and GSM. The configuration of a typical mobile communication network related to channel assignment technology is shown in FIG. 1.
Referring to FIG. 1, the mobile communication network generally includes a BSS (Base Station System) 110 and an MS (Mobile Station) 120. The BSS 110 has a radio resources management processor 112 and the MS 120, a radio resources management processor 122. The radio resources management processors 112 and 122 are usually called L3/LAC RRM/RM, where L3 refers to layer 3, LAC refers to link access control, RRM refers to radio resource management and RM refers to resource management. The radio resources management processor 112 supports the function of assigning and releasing a high-rate radio traffic channel and provides radio resources-related control.
A high-rate radio traffic channel can transmit data on a kbps to Mbps level and the number of radio traffic channels is limited within a given frequency band for radio communication.
FIG. 2 is a flowchart illustrating a conventional radio traffic channel assigning procedure. Referring to FIG. 2, upon receipt of a supplemental channel assignment message (SCAM) from a BSS in step 210, an MS determines whether the SCAM satisfies conditions A and B in steps 212 and 222. Condition A is considered in two parts: one is that there is a radio traffic channel assigned by a previous SCAM and having a duration time that has not expired; and the other is that the channel identifier (ID) of the existing radio traffic channel is identical to that of a newly assigned radio traffic channel. Condition B is that traffic is being transmitted on the existing radio traffic channel.
If condition A is not satisfied in step 212, the MS waits until a start time set in the received SCH in step 214. Condition A is not satisfied in the case where the radio traffic channel assigned by the previous SCAM and having a duration time that has not expired does not exist, or in the case where the channel IDs of the newly assigned radio traffic channel and the existing radio traffic channel are different. If the start time comes in step 216, traffic is transmitted between the MS and the BSS on the radio traffic channel assigned by the received SCAM in step 218. If the start time does not come in step 216, the process returns to step 214 to wait for the start time. If the duration time of the assigned radio traffic channel expires, the MS releases the radio traffic channel in step 220.
On the other hand, if condition A is satisfied, the MS determines whether condition B is satisfied in step 222. If condition B is satisfied, the received SCAM is in effect after the existing radio traffic channel is released. That is, when traffic transmission on the existing radio traffic channel is completed, the MS waits until the start time set in the received SCAM and transmits/receives traffic for the duration time of the new radio traffic channel. This operation is executed in step 224 and this radio traffic channel assignment is shown in FIG. 3. As shown in FIG. 3, if the start time set in the present SCAM is after the end of the duration time set in the previous SCAM, the MS can service data transmission related with the SCAMs. Following execution of step 224, the process returns to step 214.
If condition B is not satisfied in step 222, the MS discards the previous SCAM in step 226, returns to step 214, waits until the start time set in the present SCAM in step 216, and then transmits traffic on for the duration time in step 218. This radio traffic channel assignment is shown in FIG. 4. As shown in FIG. 4, if the present SCAM has arrived before the start time set in the previous SCAM, the MS neglects the previous SCAM and services data transmission related with the present SCAM. In this case, although the start time set in the present SCAM is after the end of the duration time set in the previous SCAM, the previous SCAM becomes void and thus its related data transmission is not performed.
The above conventional radio traffic channel assigning method has problems caused by circuit type channel assignment. In FIG. 4, one SCAM is stored in one time period. Although two SCAMs with different start times are received in a T0-T1 time period, the earlier SCAM is neglected and only the later SCAM is stored. In this respect, the conventional channel assigning methods cannot follow the developmental trend that the BSS gets more intelligent and the efficiency of radio traffic channels is increased along with the data-oriented development of the radio communication network. Returning to FIG. 4, although the BSS additionally assigns a T3-T4 period to the MS based on an estimate of the future radio situation after it assigns a T1-T3 period to the MS, the earlier assignment is neglected if the two SCAMs arrive before the start time set in the first SCAM. As a result, only the T3-T4 period is available to the MS, thereby dissipating radio resources.
Besides, if a SCAM requesting assignment of the same SCH arrives after data communication is completed on the SCH assigned by a previous SCAM, the existing SCH is still maintained. This is another cause of the radio resources dissipation.